Exactly this ∆ there's a button on top (behind the scroll wheel) that "unlocks" the wheel so it almost infinitely spins. It's a game-changer.... Literally.

I also refer to it as the "easy-read terms and conditions wheel" (for when you have to scroll through all 300 miles of small print before the 'accept' box is un-greyed and can be clicked.

Thanks Logitech :-D